I saw that on the Bernat website a while ago. It actually made me giggle, me being the horrible person I am. It gives me this mental image of setting your clothes out, stepping into the shower, and then coming back to find your shirt in a smouldering heap and your cat looking perturbed.
Of course, that's just my imagination going off on me. I wouldn't be laughing if I knew of anyone who had actually been hurt by, er... spontaneously combusting garments.